How to Freeze Water While Boiling

Introduction: How to Freeze Water While Boiling

This can actually happen. It seems unnatural, but the laws of physics don't lie. Liquids require heat to boil, and if the conditions are right one liquid can be boiled in order to freeze a second. Under a vacuum, the water in an acetone/water mixture can freeze while the acetone boils. Watch the video and see for yourself.

How to do this
Fill flask with 25mL of acetone and 10mL of water
place in a bell jar with a vacuum and turn on

One ought to be able to do this with water alone and eliminate the fire hazards associated with acetone. But if you don't have a vessel designed for high vacuum you could get a dangerous implosion, so consider this to be a thought experiment and do not try it unless you have experience working with high vacuums.

Imagine cooling some water to just above it's freezing point at ambient pressure. Now imagine pulling a strong enough vacuum to boil the water. Water has a very high heat of evaporation, so boiling will lower the temperature of the remaining water and ice ought to start forming as the liquid boils. (Evaporation is a cooling process. That's why we need to sweat.)* Eventually you'll run out of liquid and the ice will start subliming, just like snow can in really dry cold weather.

Notice I said "ought" and "imagine" and did not specify how strong a vacuum you need. Basic thermodynamics says it ought to work if you can lower the pressure enough. But I don't plan to try it and I recommend that only people who have experience with high vacuum work even consider trying it. Implosions throw a lot of broken glass around and can kill or maim anyone nearby.

PS, I don't think you can pull a strong enough vacuum with an aspirator, no matter how strong the flow, because the water in the aspirator would boil before the water in your sample. One would need a strong vacuum pump, vacuum grade equipment and the experience to use it safely. Or one could get an astronaut to try it during a space walk.

* The fact that water expands upon freezing will help because that means that lowering the pressure will raise the freezing point.

you can also get acetone in just about any hardware store... or the section in wal-mart that sells make-up. they have it in a plastic bottle along side fingernail polish. the metal quart costs about 6 bucks, the lil plastic bottle is only about 3.

Heat is not required for water to boil. Boiling is merely the vapor pressure of the liquid equalizing the partial pressure. Hence, water can boil at far below it's standard boiling point of 100C if you reduce pressure. Look up the gas laws and the triple point chart for H2O.

Perhaps a raise in temperature is not required to boil a liquid, but heat is still required. That's why letting off the pressure of compressed gases cools them down: the phase change from liquid to gas is endothermic and takes heat from the surroundings, causing (for example) the frost on the lighter refill can.

Acetone used to be found in finger nail polish remover. I think some types still contain it. It is great for cleaning certain types of mechanical parts when grease has dried into a solid state. I havent purchased any in a long time.